Former Boston Celtics guard Dennis Johnson, coach of the Celtics' team in the NBA Development League, collapsed during practice Thursday and died, ESPN The Magazine's Ric Bucher is reporting.

Johnson was 52.

Johnson was the MVP of the 1979 NBA Finals, averaging 22.6 points as his SuperSonics beat the Washington Bullets.

After a brief stint with the Phoenix Suns, Johnson rejoined the Boston Celtics, where he teamed with Larry Bird, Kevin McHale, Danny Ainge and Robert Parish for a glorious run in the 1980s that saw Boston win the 1984 and 1986 NBA championships.

Known throughout the league as "DJ," Johnson played in five NBA All-Star games and was named to the All-Defensive First Team six times.